The present invention relates to an electric compressor including an electric motor.
An electric compressor includes an electric motor, which is accommodated in a sealed housing. A sealed terminal is arranged on the housing to electrically connect a lead wire of the electric motor and an inverter, which is arranged outside the housing to drive the electric motor. The sealed terminal includes a terminal pin, which is formed from a conductive material, and a metal terminal holder, which holds the terminal pin. An insulative material, such as a ceramic or glass, is arranged between the terminal pin and the terminal holder.
Japanese Patent No. 3910327 (refer to FIG. 5 of the publication) discloses an example of an electric compressor that accommodates a motor and a compression mechanism, which is driven by the motor, in a metal shell. The electric compressor includes a power terminal that is connected by a flag terminal to a lead wire of the motor. To insulate the power terminal of the above publication from a metal terminal base, which forms a metal casing of the electric compressor together with the metal shell, the power terminal is coupled by a glass insulative member and a ceramic insulator to the metal terminal base. The glass insulative member is arranged at the outer side of the metal terminal base. The ceramic insulator is arranged at the inner side of the metal terminal base, that is, inside the metal shell accommodating the motor.
Japanese Laid-Open Patent Publication No. 63-230972 discloses an electric compressor, as a prior art, including a casing that accommodates motor and compression elements. The motor includes a rotor and a stator. The electric compressor includes a sealed terminal fixed to a side wall of the casing. The sealed terminal includes a cup-shaped body, a pin, and a glass seal (insulator) that fastens the pin to the body. Further, Japanese Laid-Open Patent Publication No. 63-230972 describes a problem of the prior art in which heating of the electric elements may carbonize insulative material or lubrication oil and form carbon on the insulator of the sealed terminal in the casing. Since carbon is a good conductor, the carbonization may adversely affect insulation. Thus, in the invention of Japanese Laid-Open Patent Publication No. 63-230972, a cylindrical portion is arranged on a ceramic cluster, which is coupled to the lead wire of the motor elements. The cylindrical portion of the cluster is fitted to an inner wall of the cup-shaped body to cover the glass seal of the sealed terminal and prevent the application of carbon.
In an electric compressor, refrigerant supplied to a compression mechanism is also circulated through the electric motor. In a scroll type electric compressor, for example, a large amount of fine abrasive particles may be contained in the refrigerant and circulated. Fine abrasive particles are produced by wear of portions of the scroll plated with metal or wear of metal components in the electric compressor and an external refrigerant pipe.
In the electric compressor of Japanese Patent No. 3910327, when the ceramic insulator of the power terminal arranged in the electric compressor is exposed to the circulating refrigerant, the fine abrasive particles in the refrigerant are apt to entering and collecting in fine pores of the ceramic insulator. The abrasive particles deposited on the power terminal may cause short-circuiting between the power terminal and the metal terminal base, to which the power terminal is coupled. This may result in the leakage of electric current to the metal casing of the electric compressor.
In the electric compressor of Japanese Laid-Open Patent Publication No. 63-230972, the cluster, which covers the glass seal used for fastening and insulation of the pin in the sealed terminal, is formed from a ceramic. Thus, in the same manner as Japanese Patent No. 3910327, a large amount of abrasive particles may be collected and deposited on the ceramic thereby causing short-circuiting between the pin and body or between the pin and casing.
In the prior art described in Japanese Laid-Open Patent Publication No. 63-230972, the glass seal, which serves as an insulative member, is arranged in the casing. Thus, abrasive particles in the refrigerant do not collect on the glass seal. However, when using the glass seal as an insulative member, a glass chip must be arranged between the body and pin. The glass chip is heated and melted for adhesion. Since the melted glass chip falls due to self-weight, the thickness of the glass seal cannot be increased. Accordingly, to obtain a sufficient insulating performance, the insulation distance can be increased by melting the glass seal for adhesion over a long distance in the axial direction of the pin inside and outside the body. However, this elongates the pin, which projects out of the body. Thus, when using an inverter to drive the electric motor, the coupling position of the inverter would be greatly separated outward from the casing. This enlarges the entire electric compressor, which is problematic.